Living Efficiently With Tom: Air Sealing with Caulk and Spray Foam
Spray foam around a new door in an old wall. This can be trimmed down once dry to allow for molding, drywall, or other material to create a finished look. I'll be writing about my adventures in energy efficient doors in a future entry.
Gaps that let outside air into your home or conditioned air out of your home make your air conditioner and heater work harder, consuming more energy and costing you money. If your air conditioner is working overtime to cool the whole neighborhood, it’s doing you no good at all.
Sealing gaps in your home’s exterior envelope — or between conditioned and unconditioned parts of your home — is an easy and effective way to cut energy costs and keep your home more comfortable. ENERGY STAR estimates that effective air sealing can save a homeowner up to 20 percent on heating and cooling costs. In a past entry, I talked about air sealing electrical outlets on exterior walls; caulk and spray foam are more general-application approaches to blocking the gaps that cause drafts.
For the purposes of this article, when I refer to "spray foam," I mean the spray cans (16 oz is a common size) for filling gaps — not the professional-scale equipment that’s used to spray attics, walls, and the like with large-area layers of closed-cell foam for insulation.
Where to Use It
Identifying drafts where conditioned air is leaking out of your house or where unconditioned air is leaking in may be as easy as feeling a draft or seeing daylight along a seam. You can also detect drafts using a candle flame, incense stick, or match and looking for the flame or smoke to flicker and dance. High-tech methods include pinpoint microphones that allow you to hear drafts and infrared thermometers that identify cold spots that could be air gaps. A professional energy auditor may have an infrared camera to take a picture of your home’s heat loss and gain.
Caulk is useful where gaps are small (narrow cracks and gaps up to a few millimeters) and where a more finished look is desired. Spray foam will fill larger gaps and expand to fill spaces, as well as provide some insulation.
Spray foam around another new door in an old wall. Here I've trimmed it down with a razor blade so it's ready for decorative molding around the door frame that will cover up the now-filled gap between the new door frame and existing wall. You can also see where I made a mess and got the yellow foam on the nice white door frame - I had to sand and repaint that.
Choose Your Weapon
There are a lot of different types of caulk and caulk-like products out there. Products are labeled to indicate where they’re best applied, so look closely at the packaging. Criteria to consider include: interior vs. exterior; wet vs. dry; and the material it’s being applied to.
Spray foam is a bit more straightforward than caulk. Some spray foam brands have different levels of expansion: high expansion for larger gaps, low expansion for around windows and doors. In certain situations, the expansion of spray foam around windows and doors can, in theory, pop the frame out of a wall. So, go for lower-expansion foam there.
Application
First off: Caulk is messy stuff; and spray foam is far messier. So these are definitely projects you’ll want to wear grungy old clothing for; a bit of spray foam will never come off fabric it’s bonded to. Since spray foam takes two or three days to come off skin and up to two weeks for finger nails, you may want to wear latex gloves. Spray foam has a magical way of getting everywhere, so you should put newspaper or a drop cloth down if you’re working over a nice rug or hardwood floor.
Though some caulk is available in squeeze tubes that work a bit like toothpaste, most come in rigid tubes that are placed in a spring-loaded caulk gun that pushes caulk out a nozzle from the back. When opening a new tube of caulk, you have to cut the tip off the nozzle. Err on the side of caution here; a smaller hole will create a slower and more manageable flow. You can always make it bigger later if it comes out too slow.
Spray foam comes in compressed cans (similar to spray paint) with a straw-like attachment. You can poke the straw back into gaps and spray the foam into deep gaps and cracks. Note that when you release the spray valve, the foam may continue to flow for a moment from the can while the foam in the straw expands. Applied foam will continue to expand for a few minutes after it’s applied. So if you fill a gap to the point of overflowing, it will become even more overflowing a few minutes later.
Getting the hang of applying caulk or spray foam in a tidy manner can take some practice. You may wish to start out in less conspicuous areas. Have plenty of paper towels or rags on hand. For caulk, you can smooth down lumps and messy spots with a paper towel, rag, or your finger. Spray foam is more difficult to control as it expands after application, but it’s easily trimmed down with a sharp knife or razor blade after it has hardened.
Some footage of me in action with spray foam was featured in a news piece aired on WUSA 9 in December 2010 (along with yet another stock home photo that looks nothing like my actual home).
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